Add functions git_config_set() and git_config_set_multivar()
The function git_config_set() does exactly what you think it does.
Given a key (in the form "core.filemode") and a value, it sets the
key to the value. Example:
git_config_set("core.filemode", "true");
The function git_config_set_multivar() is meant for setting variables which
can have several values for the same key. Example:
The third argument of the function is a POSIX extended regex which has to
match the value. If there is no key/value pair with a matching value, a new
key/value pair is added.
These commands are also capable of unsetting (deleting) entries: